Common Blue (Polyommatus icarus)

Male. Taken at Aston Upthorpe Downs, Oxon., on August 16th 2014.
(1/160th sec at f11. Approx 3x lifesize. © David Hastings)

Male underside. Taken at Whitecross Green Wood, Oxon., on May 22nd 2016.
(1/640th sec at f14. Approx 3x lifesize. © David Hastings)

Female. Taken at Smardale Gill, Cumbria, on July 5th 2016.
(1/800th sec at f14. Approx 3x lifesize. © David Hastings)

Female underside. Taken at Greenham Common, Berks, on August 4th 2013.
(1/400th sec at f11. Approx 3x lifesize. © David Hastings)

Mating pair. Taken at Aston Upthorpe Down, Oxon., on August 14th 2011.
(1/200th sec at f13. Approx 3x lifesize. © David Hastings)


Wing span: 29 - 36 mm

This butterfly is the commonest blue found in the British Isles. The male has violet-blue uppersides, whereas the female is usually primarily brown in colour, with a variable amount of blue on the forewings. Females usually have orange dots on the wing edges, which are absent in the male.

It can be found throughout the British Isles, although it is absent from land higher then 1500 ft in Wales and Scotland.

It is found in a wide variety of habitats, including unimproved grassland such as roadside verges and waste ground, downland, woodland clearings, heathland and even sand dunes.

This species has two broods in the southern counties of England, and one brood further north. There may be a third brood in favourable years. Time of emergence is highly variable. In good years, adults may be seen as early as the middle of May on the more southerly sites. These peak at the end of May, giving rise to a second generation that emerges in the second half of July, peaking in the middle of August. The larva is the over-wintering stage.

The main foodplant is Common Bird's-foot Trefoil. Black Medick, Common Restharrow, Greater Bird's-foot Trefoil, Lesser Trefoil and White Clover are also used.

Adults feed primarily on Bird's-foot Trefoil, Bugle, Fleabane, Kidney Vetch, Knapweeds, Marjoram, Ragwort, Thistles, Thyme, Vetches and White Clover.

The Brown Argus and Common Blue can be differentiated from their undersides, since the Brown Argus lacks a spot on the underside of the forewing that is present in the Common Blue. The Brown Argus and female Common Blue can be difficult to tell apart from their uppersides. However, the Brown Argus is completely lacking in blue scales, although it may have a blue sheen. The highly-variable female Common Blue, on the other hand, always has some blue scaling, especially close to the body.

This species is of Least Concern on the UK list.


28-Sep-2019 : Otmoor, Oxon (1)
29-Aug-2019 : Otmoor, Oxon (3)
28-Aug-2019 : Chimney Meadows, Oxon (8)
25-Aug-2019 : Farmoor Reservoir, Oxon (2)
24-Aug-2019 : Crookham Common, Berks (1)
22-Aug-2019 : Aston Rowant NNR, Oxon (10)
13-Aug-2019 : Bowdown Wood, Berks (1)
13-Aug-2019 : Greenham Common, Berks (4)
12-Aug-2019 : Otmoor, Oxon (5)
11-Aug-2019 : Farmoor Reservoir, Oxon (1)
08-Aug-2019 : Otmoor, Oxon (5)
08-Aug-2019 : Whitecross Green Wood, Oxon (7)
04-Aug-2019 : Fence Wood, Berks (2)
04-Aug-2019 : Greenham Common, Berks (2)
03-Aug-2019 : Lardon Chase, Berks (3)
02-Aug-2019 : Farmoor Reservoir, Oxon (1)
31-Jul-2019 : Aston Rowant NNR, Oxon (4)
29-Jul-2019 : Allotment, Abingdon, Oxon (1)
25-Jul-2019 : Allotment, Abingdon, Oxon (1)
21-Jul-2019 : Aston Rowant NNR, Oxon (1f)
21-Jul-2019 : Watlington Hill, Oxon (2m)
15-Jul-2019 : Lardon Chase, Berks (5)
10-Jul-2019 : Aston Upthorpe Downs, Oxon (3)
08-Jul-2019 : Bernwood Forest, Bucks (2)
30-Jun-2019 : Fence Wood, Berks (1)
29-Jun-2019 : Aston Rowant NNR, Oxon (2)
28-Jun-2019 : Dry Sandford Pit, Oxon (1)
27-Jun-2019 : Standlake Common, Oxon (2)
24-Jun-2019 : Otmoor, Oxon (7)
22-Jun-2019 : Bernwood Forest, Bucks (2)
22-Jun-2019 : Whitecross Green Wood, Oxon (5)
22-Jun-2019 : Waterperry Wood, Oxon (2)
20-Jun-2019 : Daneway Banks, Gloucs (10)
18-Jun-2019 : Barton Fields, Abingdon, Oxon (2)
16-Jun-2019 : Otmoor, Oxon (8m)
16-Jun-2019 : Whitecross Green Wood, Oxon (3m,1f)
15-Jun-2019 : Dry Sandford Pit, Oxon (3m)
09-Jun-2019 : Farmoor Reservoir, Oxon (1m)
06-Jun-2019 : Stockbridge Down, Hants (4m)
06-Jun-2019 : Bentley Wood, Wilts (7m)
03-Jun-2019 : Otmoor, Oxon (12)
03-Jun-2019 : Whitecross Green Wood, Oxon (5)
02-Jun-2019 : Radley Lakes, Oxon (4m)
01-Jun-2019 : Ardley Quarry, Oxon (4m)
01-Jun-2019 : Bucknell Wood, Northants (1f)
27-May-2019 : Lardon Chase, Berks (9m,5f)
14-May-2019 : Pewsey Downs NNR, Wilts (3m)

27-Sep-2018 : Chimney Meadows, Oxon (12+)
09-Sep-2018 : Farmoor Reservoir, Oxon (1)
06-Sep-2018 : Otmoor, Oxon (1)
04-Sep-2018 : Radley Lakes, Oxon (5)
20-Aug-2018 : Otmoor, Oxon (16)
09-Aug-2018 : Sandford Brake, Oxon (3)
07-Aug-2018 : Aston Rowant NNR, Oxon (100+)
06-Aug-2018 : Otmoor, Oxon (50+)
05-Aug-2018 : Radley Lakes, Oxon (5)
02-Aug-2018 : Lid's Down, Oxon (38+)
02-Aug-2018 : Lardon Chase, Berks (95+)
31-Jul-2018 : Whitecross Green Wood, Oxon (20)
31-Jul-2018 : Otmoor, Oxon (6)
27-Jul-2018 : Allotment, Abingdon, Oxon (1)
25-Jul-2018 : Vercors Natural Park, France
23-Jul-2018 : Vercors Natural Park, France
22-Jul-2018 : Vercors Natural Park, France
21-Jul-2018 : Vercors Natural Park, France
19-Jul-2018 : Vercors Natural Park, France
14-Jul-2018 : Aston Rowant NNR, Oxon (2m)
14-Jul-2018 : Watlington Hill, Oxon (8m,1f)
12-Jul-2018 : Cothill Fen, Oxon (1)
12-Jul-2018 : Dry Sandford Pit, Oxon (2)
10-Jul-2018 : Fence Wood, Berks (1)
10-Jul-2018 : Greenham Common, Berks (7)
07-Jul-2018 : Besselsleigh Wood, Oxon (1)
04-Jul-2018 : Aston Rowant NNR, Oxon (1f)
27-Jun-2018 : Gait Barrows NNR, Lancashire (1)
27-Jun-2018 : Arnside Knott, Cumbria (2)
21-Jun-2018 : Daneway Banks, Gloucs (13)
21-Jun-2018 : Whelford Pools, Glos (1)
15-Jun-2018 : Dry Sandford Pit, Oxon (2m)
14-Jun-2018 : Aston Rowant NNR, Oxon (13m,3f)
11-Jun-2018 : Dry Sandford Pit, Oxon (1m,4f)
06-Jun-2018 : Whitecross Green Wood, Oxon (3m,1f)
06-Jun-2018 : Otmoor, Oxon (1m)
03-Jun-2018 : Stockbridge Down, Hants (10m,1f)
03-Jun-2018 : Allotment, Abingdon, Oxon (1m)
02-Jun-2018 : Farmoor Reservoir, Oxon (5m)
27-May-2018 : Ardley Quarry, Oxon (17m)
27-May-2018 : Bucknell Wood, Northants (1m)
26-May-2018 : Lardon Chase, Berks (12m)
26-May-2018 : The Holies, Berks (30m,2f)
22-May-2018 : Dry Sandford Pit, Oxon (4m)
20-May-2018 : Pewsey Downs NNR, Wilts (5)
15-May-2018 : Lardon Chase, Berks (2)
11-Mar-2018 : Fuerteventura, Canary Islands

20-Sep-2017 : Portland Bill, Dorset (1)
20-Sep-2017 : Cheyne Weare, Portland, Dorset (1)
19-Sep-2017 : Portland Bill, Dorset (2)
31-Aug-2017 : Farmoor Reservoir, Oxon (1)
29-Aug-2017 : Lollingdon Hill, Oxon (2)
29-Aug-2017 : Lid's Down, Oxon (2)
27-Aug-2017 : Standlake Common, Oxon (2)
26-Aug-2017 : Otmoor, Oxon (12)
24-Aug-2017 : Pewsey Downs NNR, Wilts (8m,1f)
20-Aug-2017 : Farmoor Reservoir, Oxon (5)
17-Aug-2017 : Lardon Chase, Berks (12)
16-Aug-2017 : Whitecross Green Wood, Oxon (1m,2f)
16-Aug-2017 : Otmoor, Oxon (1m)
15-Aug-2017 : Whitecross Green Wood, Oxon (10m,1f)
11-Aug-2017 : Bucknell Wood, Northants (4)
10-Aug-2017 : Farmoor Reservoir, Oxon (7m,1f)
06-Aug-2017 : Dry Sandford Pit, Oxon (7)
03-Aug-2017 : Whitecross Green Wood, Oxon (2)
03-Aug-2017 : Otmoor, Oxon (2)
29-Jul-2017 : Standlake Common, Oxon (1)
23-Jul-2017 : Aston Rowant NNR, Oxon (50+)
18-Jul-2017 : Greenham Common, Berks (18+)
18-Jul-2017 : Allotment, Abingdon, Oxon (1)
16-Jul-2017 : Allotment, Abingdon, Oxon (1)
08-Jul-2017 : Aston Upthorpe Downs, Oxon (4m)
14-Jun-2017 : Daneway Banks, Gloucs (15+)
14-Jun-2017 : Dry Sandford Pit, Oxon (1)
11-Jun-2017 : Velebits National Park, Croatia
08-Jun-2017 : Paklenica National Park, Croatia
07-Jun-2017 : Irinovac, Croatia
07-Jun-2017 : Bjelopolje, Croatia
03-Jun-2017 : Dry Sandford Pit, Oxon (4m,1f)
03-Jun-2017 : Abingdon, Oxon (3m)
28-May-2017 : Pewsey Downs NNR, Wilts (8m,2f)
14-May-2017 : Whelford Pools, Glos (1m)
14-May-2017 : Rodborough Common, Glos (3m)

18-Sep-2016 : Otmoor, Oxon (3m)
29-Aug-2016 : Aston Rowant NNR, Oxon (20m,7f)
21-Aug-2016 : Hackpen Hill, Oxon (9m,4f)
14-Aug-2016 : Whitecross Green Wood, Oxon (3m,1f)
07-Aug-2016 : Cothill Fen, Oxon (1m)
06-Aug-2016 : Greenham Common, Berks (35+m,1f)
30-Jul-2016 : Aston Rowant NNR, Oxon (4m,1f)
19-Jul-2016 : Allotment, Abingdon, Oxon (1)
11-Jul-2016 : Whitecross Green Wood, Oxon (2m)
09-Jul-2016 : Dry Sandford Pit, Oxon (1m)
05-Jul-2016 : Smardale Gill NNR, Cumbria (8m,2f)
03-Jul-2016 : Arnside Knott, Cumbria (1m)
03-Jul-2016 : Gait Barrows NNR, Lancashire (1m)
02-Jul-2016 : Allithwaite Quarry, Cumbria (2)
30-Jun-2016 : Aston Rowant NNR, Oxon (2)
25-Jun-2016 : Daneway Banks, Gloucs (2m)
19-Jun-2016 : Whitecross Green Wood, Oxon (1f)
02-Jun-2016 : Lymington-Keyhaven NR, Hants (1m)
29-May-2016 : Pewsey Downs NNR, Wilts (2)
28-May-2016 : Wicken Wood, Bucks (1m,1f)
28-May-2016 : Ardley Quarry, Oxon (9m,1f)
22-May-2016 : Goring Railway Bridge, Oxon (1m)
22-May-2016 : Lardon Chase, Berks (7m,2f)

19-Sep-2015 : Dry Sandford Pit, Oxon (2m)
13-Sep-2015 : Farmoor Reservoir, Oxon (3m)
07-Sep-2015 : Otmoor, Oxon (9m,1f)
06-Sep-2015 : Farmoor Reservoir, Oxon (3m)
30-Aug-2015 : Farmoor Reservoir, Oxon (1m)
29-Aug-2015 : Lardon Chase, Berks (7m,1f)
22-Aug-2015 : Aston Rowant NNR, Oxon (30+)
22-Aug-2015 : Yeosden Bank, Bucks (19+)
21-Aug-2015 : Marston Meadows, Oxon (1m)
16-Aug-2015 : Pewsey Downs NNR, Wilts (13m)
16-Aug-2015 : Hackpen Hill, Oxon (10m)
15-Aug-2015 : Rushy Common, Oxon (13m,4f)
09-Aug-2015 : Aston Upthorpe Downs, Oxon (30m,2f)
08-Aug-2015 : Dry Sandford Pit, Oxon (24m,6f)
06-Aug-2015 : Marston Meadows, Oxon (1m,1f)
02-Aug-2015 : Otmoor, Oxon (20m,1f)
02-Aug-2015 : Bernwood Meadows, Bucks (13m)
30-Jul-2015 : Aston Rowant NNR, Oxon (5m)
26-Jul-2015 : Bansko meadows, Bulgaria
23-Jul-2015 : Mesta River fishponds, Bulgaria
23-Jul-2015 : nr Novo Hodzhovo, Bulgaria
21-Jul-2015 : nr Petrovo, Bulgaria
21-Jul-2015 : Rupite Hot Springs, Bulgaria
20-Jul-2015 : nr Samokov, Bulgaria
20-Jul-2015 : Kresna Gorge, Bulgaria
18-Jul-2015 : Crookham Common, Berks (2m)
11-Jul-2015 : Aston Upthorpe Downs, Oxon (3)
04-Jul-2015 : Calvert Jubilee, Bucks (1f)
03-Jul-2015 : Bernwood Forest, Bucks (1m)
21-Jun-2015 : Whitecross Green Wood, Oxon (3m,1f)
16-Jun-2015 : Heddon Valley, Devon (3m)
15-Jun-2015 : Collard Hill, Somerset (2m,1f)
07-Jun-2015 : Goring Railway Bridge, Oxon (2m)
07-Jun-2015 : Aston Upthorpe Downs, Oxon (27m,3f)
07-Jun-2015 : Lardon Chase, Berks (5m,1f)
06-Jun-2015 : Dry Sandford Pit, Oxon (1m)
04-Jun-2015 : Marston Meadows, Oxon (3m,1f)
30-May-2015 : Aston Rowant NNR, Oxon (20+m,3f)
28-May-2015 : Marston Meadows, Oxon (1m)
23-May-2015 : Dry Sandford Pit, Oxon (4m)
16-May-2015 : Pitstone, Bucks (3m,1f)